The present invention relates to the measurement of the grip or grasp strength of the human hand and, in particular, to an apparatus that measures the grip strength of the human hand. Such an apparatus has numerous benefits including medical uses such as the diagnosis of motor function weaknesses in the hand and ergonomic uses such as aiding in the design of tools that are more responsive to the forces applied by a hand.
Current similar devices for the measurement of grip strength generally use hydraulics to sense the magnitude of the force applied. A problem with this method of sensing force is that the hydraulic fluid will absorb some of the force, resulting in an inaccurate measurement. In addition, some new electromechanical devices use handles that deflect substantially when placed under a large grip load. The result is that these devices also absorb some force and are therefore not isometric in the measurement of grip strength.
During the gripping of the device, more than one grip load is simultaneously applied to the device. The ability to accurately distinguish between the primary load and cross loads is extremely important to a precise evaluation of grip strength. A problem with the current devices for measuring grip strength is that they do not distinguish between the various components of the grip load. The result is a decrease in the accuracy of their measurement.
In addition, currently used devices are not capable of determining the location of the resultant force acting on the device and do not measure the contribution of each digit to the total grip load.